THE INTERACTIONS OF FERRIC AND FERROUS CYTOCHROME-C WITH CARDIOLIPIN IN PHOSPHOLIPID-MEMBRANES STUDIED BY SOLID-STATE H-2 AND P-31 NMR

The interactions of ferric and ferrous cytochrome c with cardiolipin ( CL) in lipid bilayers were investigated by solid-state H-2 and P-31 NM R. To examine the effect of the interaction on the glycerol backbone o f CL, its glycerol moiety was specifically deuterated. H-2 NMR experim ent showed that only ferricytochrome c interacts strongly with CL in t he CL bilayers and binary mixed phosphatidylcholine(PC)ICL bilayers. T his was consistent with the result of cytochrome c binding experiment. Ferricytochrome c binds to CL liposomes as much as two times of ferro cytochrome c. This suggests that the charge of the heme iron is also i nvolved in the interaction. The change of the deuterium quadrupole spl itting of CL on binding of cytochrome c was larger for the single comp onent CL bilayer than for the PC/CL bilayer, suggesting that a CL doma in rather than a single molecule is responsible for the strong interac tion with cytochrome c. (C) 1998 Elsevier Science B.V.